Farm advice: Caring for cows on crop
Wintering cows on crops is a common strategy to help keep them in good condition, but there is also a risk of the animals falling sick
However, farmers are doing a number of things to reduce this risk. One of these is monitoring the herd carefully and keeping an eye out for sick cows, or those not keen to feed when the rest of the herd is feeding. Treat sick cows quickly, especially in poor weather conditions, and call your vet as soon as possible.
Providing a suitable recovery site, such as a grass paddock with good shelter and a low stocking rate, with additional highly palatable feed and water, will speed up recovery for the cow. Your vet will advise you on the best recovery plan for your stock.
Weather is a significant factor to consider when wintering cows on crop. Cattle are tolerant of cold conditions and they can make physical changes by thickening their skin and coats and drawing on their fat reserves. If a cow is clean and dry and there is little wind or rain, cold stress is rare until ambient temperatures fall below -10°C.
The factors that increase the risk of cold stress are extremely low temperatures, wind, rain and mud, low condition scores, and low feeding levels.
During periods of cold and wet, the energy required by cows can increase by at least 12 MJ ME per day depending on the severity of the conditions. Added to this increased requirement is often a decline in feed utilisation, increasing the gap between energy intake and requirement. To keep cattle in the right condition during periods of extreme winter weather, offer additional feed.
For a typical crop-based wintering diet (aiming to gain 0.5 BCS units during the dry period), in mild environmental conditions a 500 kg cow needs to eat about 124 MJ ME per day. Typical diets to provide this include:
- 9.5kg kale and 4kg average quality pasture baleage (assuming 80% utilisation of the crop and 85% utilisation of baleage).
- 9.8kg DM swede and 4kg average quality pasture baleage (assuming 80% utilisation of the crop and 85% utilisation of baleage).
- 8.3kg fodder beet and 3.5kg average quality pasture baleage (assuming 90% utilisation of the crop and 85% utilisation of baleage).
If this same cow is exposed to prolonged cold and wet conditions, then her energy requirement increases to at least 136 MJ ME per day. To achieve this increased energy requirement, assuming the same feed utilisation, either provide more crop or more supplement.
For a herd of 160 cows, this extra energy could be provided by an extra bale per day of average quality pasture silage (220kg DM equivalent, 10 ME) or additional crop:
- Kale: 160m2 for 160 cows grazing a 12T crop (1.2kg DM per cow)
- Swedes: 120m2 for 160 cows grazing a 16T crop (1.2kg DM swedes)
- Fodder beet: not recommended because it requires at least an additional 1kg
DM per cow per day, which could result in digestive upsets of some animals even when fully transitioned. Depending on the BCS of the herd and the weather situation, wet and windy conditions require an additional 0.5–3 kg DM per cow per day.
For more information, visit dairynz.co.nz.
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